do you have a rheostat/ thermostat for your UTH? i put my temp probe in the middle on the back wall of my bps cage for ambient air temp. i have a rheostat for my UTH and i measure it every morning and i measure inside the hide over the UTH and make sure everything is up to par. umm my bp is about 17 inches and i feed her small adult mice and she is fine so you can try adult mice. the mouse should be as big as the widest part of your snakes body.